There's no geographical cycle operating on that large of a time period. Ice ages repeat in tens of thousands of years, but that doesn't come close to what we need here for that to be responsible for what we're currently experiencing. When earth's climate shifts, and if it's not due to a cycle, then we're looking at massive volcanic eruptions, large meteors, and sudden changes in tectonic plates. You also have to recognize that we're seeing an increase in carbon before we see an increase in temperature, meaning that this current climate shift is caused by an increased input of carbon into the atmosphere, not sun spots or anything else.

If I had to guess, that may be as far back as they can accurately go.